I'm using an Omron NT31C HMI and a C200HG Omron PLC. I tried downloading data from the PC to the HMI (using Port A) and it was successful. I can see the screen when I go to screen display. But when I exit it and come out to the main screen of the HMI it says 'System Initializing'. My addressing on the NT support tool under PT control area is D00100 and PT notify area is D00110...I'm really not sure how addressing works in Omron as I'm used to working with AB.
AFTER downloading data to the HMI, this is how I connected everything: HMI serial port B to the PLC using an RS-232C cable and PLC to the PC using an RS-232C cable.

Btw..I'm on my last year at college and this is for my final project..i just cant get it to work :S

If memory serves correctly, Port B is for Printers/Barcode readers.
The system initialising normally means that comms are not established.
Also, I am pretty sure that you will need to make a specific cable, a standard RS232 is not quite correct (Omron swaps a few pins).

You will also need to ensure that the PLC Serial port settings match the comms method that you select in the NT.

If you get the correct cable, then connect the PLC to Port A of the NT, it all should work.

The meaning of the screen System Initializing only specify that the NT31 didn't found any connection with PLC. You could use either port A or B but you have to configure them thru the system menu(press 2 corner on the NT31 to get in) go in "Maintenance Mode" than in "Memory Switch". You will find in there the option for the port configuration. Only one of the 2 port could be activated.

Don't forget that the PLC and the NT31 must have the same setting for the comm port, once it done the communication between NT31 and PLC will start automatically.

also I beleive if memory serves correct the port must use NT link. to communicate with the PLC both the PLC and touchsceen require this to be setup. If yu have Cx-designer look under the appendixes of the setup manual. or the NS operations manual the pinouts and communication setup is covered there

For 1 to 1 You could use Host link or NT-link but it's better to use NT-link because NT-Link could work on single Bit(Read/Write) and Host link only work on the full word(16 bits).

Here a example of the problem you could have when using Host Link:
I have 2 push button on the screen. One do a SET of bit 1.00 and the other do RESET of bit 1.01
When I press the SET the bit go ON, but when I press the RESET all the bits of word 1(1.00 - 1.15) turn OFF.